Generally, in an internal combustion engine in which the valve timing of an intake valve or an exhaust valve is variable, it is necessary to constantly detect, by using a cam aperture sensor, the cam angle of a cam shaft that opens or closes the intake valve or the exhaust valve.
Patent document 1, as prior art, proposes mounting a cam shaft angle sensor to a member of a cylinder head, rather than to a head cover for covering the upper face of the cylinder head.
Specifically, a mounting portion is formed integral with a member of the cylinder head, such as a bearing cap that pivotally supports the upper half of the cam shaft, in a manner such that the mounting portion penetrates through the head cover to project beyond the upper side of the head cover. The angle sensor is removably attached to the mounting portion by being fitted into a mounting hole made in the mounting portion and fastened with a bolt.
Patent document 1: JP-A-2006-220073